[SiteSettings] Redesign with tabs

[imnasnainaec]

Resolves #1175

Implement tabs, so you don't have to scroll down past projects to manage users or banners.

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This change is 

[codecov-commenter]

Codecov Report

Patch coverage: 78.57% and project coverage change: +0.78 🎉

Comparison is base (d9d764a) 65.97% compared to head (03c1970) 66.76%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2415      +/-   ##
==========================================
+ Coverage   65.97%   66.76%   +0.78%     
==========================================
  Files         239      239              
  Lines        8215     8223       +8     
  Branches      502      504       +2     
==========================================
+ Hits         5420     5490      +70     
+ Misses       2439     2376      -63     
- Partials      356      357       +1     

Flag	Coverage Δ
backend	77.98% <ø> (+0.06%)	⬆️
frontend	53.78% <78.57%> (+1.64%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/components/App/AppLoggedIn.tsx	0.00% <ø> (ø)
...omponents/SiteSettings/ProjectManagement/index.tsx	100.00% <ø> (ø)
...c/components/SiteSettings/UserManagement/index.tsx	61.53% <ø> (ø)
...omponents/SiteSettings/UserManagement/UserList.tsx	63.33% <25.00%> (+63.33%)	⬆️
src/components/SiteSettings/Banners.tsx	75.00% <100.00%> (ø)
src/components/SiteSettings/index.tsx	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes

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[jasonleenaylor]

Reviewed 7 of 8 files at r1, 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @imnasnainaec)